The agency keeps the drug off the market, citing possible cardiovascular problems in users. This is the third weight-loss drug the agency has turned away in recent months.

Ignoring the recommendation of its own advisory committee, the Food and Drug Administration on Tuesday declined to approve the weight-loss drug Contrave, the third such drug the agency has kept off the market in recent months.

The agency concluded that the benefits of the drug — about 50% of patients were able to lose 5% of their body weight in clinical trials, compared with 10% of those receiving placebos — were not sufficient to outweigh the potential risks and the potential for abuse. Many patients receiving the drug had a slight increase in blood pressure and pulse rates.

The FDA notified the drug's manufacturer, Orexigen Therapeutics Inc. of San Diego, that it would have to conduct a large clinical trial of the drug to test for possible cardiovascular complications in the elderly and the obese before the medication could be marketed, according to a statement released by the company.

Such a trial would probably take three to five years and cost as much as $200 million. Most analysts think such a trial is probably beyond the resources of Orexigen, which is focused solely on the development of anti-obesity drugs and has no other products on the market. The company's stock fell 73% to close at $2.50 in Nasdaq trading Tuesday after the FDA announcement.

At a December meeting, the FDA advisory panel voted 13 to 7 in favor of approving Contrave, arguing that the potential cardiovascular problems could be addressed in a post-marketing study. If that had been the case, Orexigen's marketing partner, Japan's Takeda Pharmaceutical Co., would have shared in the cost of the study.

Contrave is a combination of two drugs already on the market: naltrexone, a drug used to combat alcohol and drug addiction, and bupropion, an antidepressant better known by its brand name Wellbutrin. Market analysts had predicted that, if approved, Contrave could have had yearly sales of $1.2 billion by 2018.

In October, the FDA rejected the proposed weight-loss drug Qnexa because of concerns about heart problems and birth defects. That same month, the agency rejected another experimental diet drug called Lorqess that appeared to cause tumor growth in animals. Also in October, the weight-loss drug Meridia was pulled from the market because of concerns that it boosted the rate of heart attacks and strokes.